It is actually correct, it is slower by 0.5-2x in terms of runtime resulting in a runtime of 1.5-3x. Admittedly it would probably have been less confusing to say that the runtime increased by 0.5-2x to 1.5-3x because slower is more intuitively associated with less while the runtime of course increases.
In terms of throughput it is a decrease by 0.33-0.67x to 0.67-0.33x. That this are the same numbers in reverse order is of course just a coincidence, would the runtime have increased by only 0.2-0.5x to 1.2-1.5x, then the throughput would have decreased by 0.17-0.33x to 0.83-0.67x.
In terms of throughput it is a decrease by 0.33-0.67x to 0.67-0.33x. That this are the same numbers in reverse order is of course just a coincidence, would the runtime have increased by only 0.2-0.5x to 1.2-1.5x, then the throughput would have decreased by 0.17-0.33x to 0.83-0.67x.